libSBML C++ API
5.18.0
|
This section describes libSBML's facilities for working with SBML representations of mathematical expressions.
Internally, libSBML uses Abstract Syntax Trees (ASTs) to provide a canonical, in-memory representation for all mathematical formulas regardless of their original format (i.e., C-like infix text strings or the XML-based MathML 2.0 format). LibSBML provides an extensive API for working with ASTs; it also provides facilities for translating between ASTs and mathematical formulas writing in a text-string notation, as well as translating between ASTs and MathML.
"1 + 2"
is represented as an AST with one plus node having two integer children nodes for the numbers 1
and 2
. The figure also shows the corresponding MathML representation:Infix | AST | MathML |
---|---|---|
1 + 2
|
<math xmlns="http://www.w3.org/1998/Math/MathML"> <apply> <plus/> <cn type="integer"> 1 </cn> <cn type="integer"> 2 </cn> </apply> </math>
|
The following are other noteworthy points about the AST representation in libSBML:
double
data type. This is done so that when an SBML model is read in and then written out again, the amount of change introduced by libSBML to the SBML during the round-trip activity is minimized.For many applications, the details of ASTs are irrelevant because libSBML provides text-string based translation functions such as SBML_formulaToL3String() and SBML_parseL3Formula(). If you find the complexity of using the AST representation of expressions too high for your purposes, perhaps the string-based functions will be more suitable.
SBML Levels 2 and 3 represent mathematical expressions using using MathML 2.0 (more specifically, a subset of the content portion of MathML 2.0), but most applications using libSBML do not use MathML directly. Instead, applications generally interact with mathematics using either the API for Abstract Syntax Trees (described below), or using libSBML's facilities for encoding and decoding mathematical formulas to/from text strings. The latter is simpler to use directly, so we describe it first.
The libSBML formula parser has been carefully engineered so that transformations from MathML to the libSBML infix text notation and back is possible with a minimum of disruption to the structure of the mathematical expression. The example below shows a simple program that, when run, takes a MathML string compiled into the program, converts it to an AST, converts that to an infix representation of the formula, compares it to the expected form of that formula, and finally translates that formula back to MathML and displays it. The output displayed on the terminal should have the same structure as the MathML it started with. The program is a simple example of using libSBML's basic MathML and AST reading and writing methods, and shows that libSBML preserves the ordering and structure of the mathematical expressions.
The text-string form of mathematical formulas written by SBML_formulaToString() and SBML_formulaToL3String(), and read by SBML_parseFormula() and SBML_parseL3Formula(), use a simple C-inspired infix notation. It is summarized in the next section below. A formula in this text-string form therefore can be handed to a program that understands SBML mathematical expressions, or used as part of a translation system.
There are actually two text-based formula parsing/writing systems in libSBML: one that uses a more limited syntax and was originally designed for translation between SBML Level 1 (which used a text-string format for representing mathematics) and higher levels of SBML, and a more recent, more powerful version that offers features to support SBML Level 3. We describe both below, beginning with the simpler but more limited system.
The simpler, more limited translation system is read by SBML_parseFormula() and written by SBML_formulaToString(). It uses an infix notation essentially derived from the syntax of the C programming language and was originally used in SBML Level 1. We summarize the syntax here, but for more complete details, readers should consult the documentation for SBML_parseFormula().
Formula strings in this infix notation may contain operators, function calls, symbols, and white space characters. The allowable white space characters are tab and space. The following are illustrative examples of formulas expressed in the syntax:
0.10 * k4^2
(vm * s1)/(km + s1)
The following table shows the precedence rules in this syntax. In the Class column, operand implies the construct is an operand, prefix implies the operation is applied to the following arguments, unary implies there is one argument, and binary implies there are two arguments. The values in the Precedence column show how the order of different types of operation are determined. For example, the expression a + b * c
is evaluated as a + (b * c)
because the *
operator has higher precedence. The Associates column shows how the order of similar precedence operations is determined; for example, a - b + c
is evaluated as (a - b) + c
because the +
and -
operators are left-associative. The precedence and associativity rules are taken from the C programming language, except for the symbol ^
, which is used in C for a different purpose. (Exponentiation can be invoked using either ^
or the function power
.)
Token | Operation | Class | Precedence | Associates |
---|---|---|---|---|
name | symbol reference | operand | 6 | n/a |
( expression) | expression grouping | operand | 6 | n/a |
f( ...) | function call | prefix | 6 | left |
- | negation | unary | 5 | right |
^ | power | binary | 4 | left |
* | multiplication | binary | 3 | left |
/ | divison | binary | 3 | left |
+ | addition | binary | 2 | left |
- | subtraction | binary | 2 | left |
, | argument delimiter | binary | 1 | left |
A program parsing a formula in an SBML model should assume that names appearing in the formula are the identifiers of Species, Parameter, Compartment, FunctionDefinition, (in Level 2) Reaction, or (in Level 3) SpeciesReference objects defined in a model. When a function call is involved, the syntax consists of a function identifier, followed by optional white space, followed by an opening parenthesis, followed by a sequence of zero or more arguments separated by commas (with each comma optionally preceded and/or followed by zero or more white space characters), followed by a closing parenthesis. There is an almost one-to-one mapping between the list of predefined functions available, and those defined in MathML. All of the MathML functions are recognized; this set is larger than the functions defined in SBML Level 1. In the subset of functions that overlap between MathML and SBML Level 1, there exist a few differences. The following table summarizes the differences between the predefined functions in SBML Level 1 and the MathML equivalents in SBML Levels 2 and 3:
Text string formula functions | MathML equivalents in SBML Levels 2 and 3 |
---|---|
acos | arccos |
asin | arcsin |
atan | arctan |
ceil | ceiling |
log | ln |
log10(x) | log(x) or log(10, x) |
pow(x, y) | power(x, y) |
sqr(x) | power(x, 2) |
sqrt(x) | root(x) or root(2, x) |
Note that there are differences between the symbols used to represent the common mathematical functions and the corresponding MathML token names. This is a potential source of incompatibilities. Note in particular that in this text-string syntax, log(x)
always represents the natural logarithm, whereas in MathML, the natural logarithm is <ln/>
. Application writers are urged to be careful when translating between text forms and MathML forms, especially if they provide a direct text-string input facility to users of their software systems. The more advanced mathematical formula system, described below, offers the ability to control how log
is interpreted as well as other parsing behaviors.
The following lists the main differences in the formula syntax supported by the Level 3 ("L3") versions of the formula parsers and formatters, compared to what is supported by the Level 1-oriented SBML_parseFormula() and SBML_formulaToString():
SId
in the SBML specifications). The whitespace between number and unit is optional.&&
(and), ||
(or), !
(not), and !=
(not equals) may be used.%
and will produce a <piecewise>
function in the corresponding MathML output by default, or can produce the MathML function rem
, depending on the L3ParserSettings object (see L3ParserSettings_setParseModuloL3v2() ).arc
as a prefix or simply a
; in other words, both arccsc
and acsc
are interpreted as the operator arccosecant as defined in MathML 2.0. (Many functions in the simpler SBML Level 1 oriented parser implemented by SBML_parseFormula() are defined this way as well, but not all.)(integer/integer)Spaces are not allowed in this construct; in other words, "
(3 / 4)
" (with whitespace between the numbers and the operator) will be parsed into the MathML <divide>
construct rather than a rational number. You can, however, assign units to a rational number as a whole; here is an example: "(3/4) ml
". (In the case of division rather than a rational number, units are not interpreted in this way.)The function log
with a single argument ("log(x)
") can be parsed as log10(x)
, ln(x)
, or treated as an error, as desired.
Unary minus signs can be collapsed or preserved; that is, sequential pairs of unary minuses (e.g., "- -3
") can be removed from the input entirely and single unary minuses can be incorporated into the number node, or all minuses can be preserved in the AST node structure.
Parsing of units embedded in the input string can be turned on and off.
The string avogadro
can be parsed as a MathML csymbol or as an identifier.
The string % can be parsed either as a piecewise function or as the 'rem' function: a % b
will either become
piecewise(a - b*ceil(a/b), xor((a < 0), (b < 0)), a - b*floor(a/b))
or
rem(a, b)
.
The latter is simpler, but the rem
MathML is only allowed as of SBML Level 3 Version 2.
A Model object may optionally be provided to the parser using the variant function call SBML_parseL3FormulaWithModel() or stored in a L3ParserSettings object passed to the variant function SBML_parseL3FormulaWithSettings(). When a Model object is provided, identifiers (values of type SId
) from that model are used in preference to pre-defined MathML definitions for both symbols and functions. More precisely:
In the case of symbols: the Model entities whose identifiers will shadow identical symbols in the mathematical formula are: Species, Compartment, Parameter, Reaction, and SpeciesReference. For instance, if the parser is given a Model containing a Species with the identifier "pi
", and the formula to be parsed is "3*pi
", the MathML produced will contain the construct <ci> pi </ci>
instead of the construct <pi/>
.
SId
values of user-defined functions present in the model will be used preferentially over pre-defined MathML functions. For example, if the passed-in Model contains a FunctionDefinition object with the identifier "sin
", that function will be used instead of the predefined MathML function <sin/>
. These configuration settings cannot be changed directly using the basic parser and formatter functions, but can be changed on a per-call basis by using the alternative functions SBML_parseL3FormulaWithSettings() and SBML_formulaToL3StringWithSettings().
Neither SBML nor the MathML standard define a "string-form" equivalent to MathML expressions. The approach taken by libSBML is to start with the formula syntax defined by SBML Level 1 (which in fact used a custom text-string representation of formulas, and not MathML), and expand it to include the functionality described above. This formula syntax is based mostly on C programming syntax, and may contain operators, function calls, symbols, and white space characters. The following table provides the precedence rules for the different entities that may appear in formula strings.
Token | Operation | Class | Preced. | Assoc. |
---|---|---|---|---|
name | symbol reference | operand | 8 | n/a |
( expression) | expression grouping | operand | 8 | n/a |
f( ...) | function call | prefix | 8 | left |
^ | power | binary | 7 | left |
-, ! | negation, Boolean 'not' | unary | 6 | right |
*, /, % | multip., div., modulo | binary | 5 | left |
+, - | addition and subtraction | binary | 4 | left |
==, <, >, <=, >=, != | Boolean comparisons | binary | 3 | left |
&&, || | Boolean 'and' and 'or' | binary | 2 | left |
, | argument delimiter | binary | 1 | left |
In the table above, operand implies the construct is an operand, prefix implies the operation is applied to the following arguments, unary implies there is one argument, and binary implies there are two arguments. The values in the Precedence column show how the order of different types of operation are determined. For example, the expression a + b * c
is evaluated as a + (b * c)
because the *
operator has higher precedence. The Associates column shows how the order of similar precedence operations is determined; for example, a && b || c
is evaluated as (a && b) || c
because the &&
and ||
operators are left-associative and have the same precedence.
The function call syntax consists of a function name, followed by optional white space, followed by an opening parenthesis token, followed by a sequence of zero or more arguments separated by commas (with each comma optionally preceded and/or followed by zero or more white space characters), followed by a closing parenthesis token. The function name must be chosen from one of the pre-defined functions in SBML or a user-defined function in the model. The following table lists the names of certain common mathematical functions; this table corresponds to Table 6 in the SBML Level 1 Version 2 specification with additions based on the functions added in SBML Level 2 and Level 3:
Name | Argument(s) | Formula or meaning | Argument Constraints | Result constraints |
---|---|---|---|---|
abs |
x | Absolute value of x. | ||
acos , arccos |
x | Arccosine of x in radians. | –1.0 ≤ x ≤ 1.0 | 0 ≤ acos(x) ≤ π |
acosh , arccosh |
x | Hyperbolic arccosine of x in radians. | ||
acot , arccot |
x | Arccotangent of x in radians. | ||
acoth , arccoth |
x | Hyperbolic arccotangent of x in radians. | ||
acsc , arccsc |
x | Arccosecant of x in radians. | ||
acsch , arccsch |
x | Hyperbolic arccosecant of x in radians. | ||
asec , arcsec |
x | Arcsecant of x in radians. | ||
asech , arcsech |
x | Hyperbolic arcsecant of x in radians. | ||
asin , arcsin |
x | Arcsine of x in radians. | –1.0 ≤ x ≤ 1.0 | 0 ≤ asin(x) ≤ π |
atan , arctan |
x | Arctangent of x in radians. | 0 ≤ atan(x) ≤ π | |
atanh , arctanh |
x | Hyperbolic arctangent of x in radians. | ||
ceil , ceiling |
x | Smallest number not less than x whose value is an exact integer. | ||
cos |
x | Cosine of x | ||
cosh |
x | Hyperbolic cosine of x. | ||
cot |
x | Cotangent of x. | ||
coth |
x | Hyperbolic cotangent of x. | ||
csc |
x | Cosecant of x. | ||
csch |
x | Hyperbolic cosecant of x. | ||
delay |
x, y | The value of x at y time units in the past. | ||
factorial |
n | The factorial of n. Factorials are defined by n! = n*(n–1)* ... * 1. | n must be an integer. | |
exp |
x | e x, where e is the base of the natural logarithm. | ||
floor |
x | The largest number not greater than x whose value is an exact integer. | ||
ln |
x | Natural logarithm of x. | x > 0 | |
log |
x | By default, the base 10 logarithm of x, but can be set to be the natural logarithm of x, or to be an illegal construct. | x > 0 | |
log |
x, y | The base x logarithm of y. | y > 0 | |
log10 |
x | Base 10 logarithm of x. | x > 0 | |
piecewise |
x1, y1, [x2, y2,] [...] [z] | A piecewise function: if (y1), x1. Otherwise, if (y2), x2, etc. Otherwise, z. | y1, y2, y3 [etc] must be Boolean | |
pow , power |
x, y | x y. | ||
root |
b, x | The root base b of x. | ||
sec |
x | Secant of x. | ||
sech |
x | Hyperbolic secant of x. | ||
sqr |
x | x2. | ||
sqrt |
x | √x. | x > 0 | sqrt(x) ≥ 0 |
sin |
x | Sine of x. | ||
sinh |
x | Hyperbolic sine of x. | ||
tan |
x | Tangent of x. | x ≠ n*π/2, for odd integer n | |
tanh |
x | Hyperbolic tangent of x. | ||
and |
x, y, z... | Boolean and(x, y, z...): returns true if all of its arguments are true. Note that and is an n-ary function, taking 0 or more arguments, and that and() returns true . |
All arguments must be Boolean | |
not |
x | Boolean not(x) | x must be Boolean | |
or |
x, y, z... | Boolean or(x, y, z...): returns true if at least one of its arguments is true. Note that or is an n-ary function, taking 0 or more arguments, and that or() returns false . |
All arguments must be Boolean | |
xor |
x, y, z... | Boolean xor(x, y, z...): returns true if an odd number of its arguments is true. Note that xor is an n-ary function, taking 0 or more arguments, and that xor() returns false . |
All arguments must be Boolean | |
eq |
x, y, z... | Boolean eq(x, y, z...): returns true if all arguments are equal. Note that eq is an n-ary function, but must take 2 or more arguments. |
||
geq |
x, y, z... | Boolean geq(x, y, z...): returns true if each argument is greater than or equal to the argument following it. Note that geq is an n-ary function, but must take 2 or more arguments. |
||
gt |
x, y, z... | Boolean gt(x, y, z...): returns true if each argument is greater than the argument following it. Note that gt is an n-ary function, but must take 2 or more arguments. |
||
leq |
x, y, z... | Boolean leq(x, y, z...): returns true if each argument is less than or equal to the argument following it. Note that leq is an n-ary function, but must take 2 or more arguments. |
||
lt |
x, y, z... | Boolean lt(x, y, z...): returns true if each argument is less than the argument following it. Note that lt is an n-ary function, but must take 2 or more arguments. |
||
neq |
x, y | Boolean x != y: returns true unless x and y are equal. |
||
plus |
x, y, z... | x + y + z + ...: The sum of the arguments of the function. Note that plus is an n-ary function taking 0 or more arguments, and that plus() returns 0 . |
||
times |
x, y, z... | x * y * z * ...: The product of the arguments of the function. Note that times is an n-ary function taking 0 or more arguments, and that times() returns 1 . |
||
minus |
x, y | x – y. | ||
divide |
x, y | x / y. |
Parsing of the various MathML functions and constants are all case-insensitive by default: function names such as cos
, Cos
and COS
are all parsed as the MathML cosine operator, <cos>
. However, when a Model object is used in conjunction with either SBML_parseL3FormulaWithModel() or SBML_parseL3FormulaWithSettings(), any identifiers found in that model will be parsed in a case-sensitive way. For example, if a model contains a Species having the identifier Pi
, the parser will parse "Pi
" in the input as "<ci> Pi </ci>
" but will continue to parse the symbols "pi
" and "PI
" as "<pi>
".
As mentioned above, the manner in which the "L3" versions of the formula parser and formatter interpret the function "log
" can be changed. To do so, callers should use the function SBML_parseL3FormulaWithSettings() and pass it an appropriate L3ParserSettings object. By default, unlike the SBML Level 1 parser implemented by SBML_parseFormula(), the string "log
" is interpreted as the base 10 logarithm, and not as the natural logarithm. However, you can change the interpretation to be base-10 log, natural log, or as an error; since the name "log" by itself is ambiguous, you require that the parser uses log10
or ln
instead, which are more clear. Please refer to SBML_parseL3FormulaWithSettings().
In addition, the following symbols will be translated to their MathML equivalents, if no symbol with the same SId
identifier string exists in the Model object provided:
Name | Meaning | MathML |
---|---|---|
true |
Boolean value true |
<true/> |
false |
Boolean value false |
<false/> |
pi |
Mathematical constant pi | <pi/> |
avogadro |
Value of Avogadro's constant stipulated by SBML | <csymbol encoding="text" definitionURL="http://www.sbml.org/sbml/symbols/avogadro"> avogadro </csymbol/> |
time |
Simulation time as defined in SBML | <csymbol encoding="text" definitionURL="http://www.sbml.org/sbml/symbols/time"> time </csymbol/> |
inf , infinity |
Mathematical constant "infinity" | <infinity/> |
nan , notanumber |
Mathematical concept "not a number" | <notanumber/> |
Again, as mentioned above, whether the string "avogadro
" is parsed as an AST node of type AST_NAME_AVOGADRO or AST_NAME is configurable; use the version of the parser function called SBML_parseL3FormulaWithSettings(). This Avogadro-related functionality is provided because SBML Level 2 models may not use AST_NAME_AVOGADRO AST nodes.
While it is convenient to read and write mathematical expressions in the form of text strings, advanced applications usually need more powerful ways of creating, traversing, and modifying mathematical formulas. For this reason, libSBML provides a rich API for interacting with ASTs directly. This section summarizes these facilities; for more information, readers should consult the documentation for the ASTNode class.
AST_CONSTANT_E | AST_FUNCTION_CSC | AST_LOGICAL_AND |
AST_CONSTANT_FALSE | AST_FUNCTION_CSCH | AST_LOGICAL_IMPLIES2 |
AST_CONSTANT_PI | AST_FUNCTION_DELAY | AST_LOGICAL_NOT |
AST_CONSTANT_TRUE | AST_FUNCTION_EXP | AST_LOGICAL_OR |
AST_DIVIDE | AST_FUNCTION_FACTORIAL | AST_LOGICAL_XOR |
AST_FUNCTION | AST_FUNCTION_FLOOR | AST_MINUS |
AST_FUNCTION_ABS | AST_FUNCTION_LN | AST_NAME |
AST_FUNCTION_ARCCOS | AST_FUNCTION_LOG | AST_NAME_AVOGADRO1 |
AST_FUNCTION_ARCCOSH | AST_FUNCTION_MAX2 | AST_NAME_TIME |
AST_FUNCTION_ARCCOT | AST_FUNCTION_MIN2 | AST_ORIGINATES_IN_PACKAGE2 |
AST_FUNCTION_ARCCOTH | AST_FUNCTION_PIECEWISE | AST_PLUS |
AST_FUNCTION_ARCCSC | AST_FUNCTION_POWER | AST_POWER |
AST_FUNCTION_ARCCSCH | AST_FUNCTION_QUOTIENT2 | AST_RATIONAL |
AST_FUNCTION_ARCSEC | AST_FUNCTION_RATE_OF2 | AST_REAL |
AST_FUNCTION_ARCSECH | AST_FUNCTION_REM2 | AST_REAL_E |
AST_FUNCTION_ARCSIN | AST_FUNCTION_ROOT | AST_RELATIONAL_EQ |
AST_FUNCTION_ARCSINH | AST_FUNCTION_SEC | AST_RELATIONAL_GEQ |
AST_FUNCTION_ARCTAN | AST_FUNCTION_SECH | AST_RELATIONAL_GT |
AST_FUNCTION_ARCTANH | AST_FUNCTION_SIN | AST_RELATIONAL_LEQ |
AST_FUNCTION_CEILING | AST_FUNCTION_SINH | AST_RELATIONAL_LT |
AST_FUNCTION_COS | AST_FUNCTION_TAN | AST_RELATIONAL_NEQ |
AST_FUNCTION_COSH | AST_FUNCTION_TANH | AST_TIMES |
AST_FUNCTION_COT | AST_INTEGER | AST_UNKNOWN |
AST_FUNCTION_COTH | AST_LAMBDA | |
1 (Level 3 only) | ||
2 (Level 3 Version 2+ only) |
The types have the following meanings:
"+"
), then the node's type will be AST_PLUS, AST_MINUS, AST_TIMES, AST_DIVIDE, or AST_POWER, as appropriate.AST_FUNCTION_
X, AST_LOGICAL_
X, or AST_RELATIONAL_
X, as appropriate. (Examples: AST_FUNCTION_LOG, AST_RELATIONAL_LEQ.)"ExponentialE"
, "Pi"
, "True"
or "False"
), then the node's type will be AST_CONSTANT_E, AST_CONSTANT_PI, AST_CONSTANT_TRUE, or AST_CONSTANT_FALSE.time
, the value of the node will be AST_NAME_TIME. (Note, however, that the MathML csymbol delay
is translated into a node of type AST_FUNCTION_DELAY. The difference is due to the fact that time
is a single variable, whereas delay
is actually a function taking arguments.)avogadro
, the value of the node will be AST_NAME_AVOGADRO.rateOf
, the value of the node will be AST_FUNCTION_RATE_OF.ASTNodeType_t getType()
returns the type of this AST node. bool isConstant()
returns true
if this AST node is a MathML constant (true
, false
, pi
, exponentiale
), false
otherwise. bool isBoolean()
returns true
if this AST node returns a Boolean value (by being either a logical operator, a relational operator, or the constant true
or false
). bool isFunction()
returns true
if this AST node is a function (i.e., a MathML defined function such as exp
or else a function defined by a FunctionDefinition in the Model). bool isInfinity()
returns true
if this AST node is the special IEEE 754 value infinity. bool isInteger()
returns true
if this AST node is holding an integer value. bool isNumber()
returns true
if this AST node is holding any number. bool isLambda()
returns true
if this AST node is a MathML lambda
construct. bool isLog10()
returns true
if this AST node represents the log10
function, specifically, that its type is AST_FUNCTION_LOG
and it has two children, the first of which is an integer equal to 10. bool isLogical()
returns true
if this AST node is a logical operator (and
, or
, not
, xor
). bool isName()
returns true
if this AST node is a user-defined name or (in SBML Levels 2 and 3) one of the two special csymbol
constructs "delay" or "time". bool isNaN()
returns true
if this AST node has the special IEEE 754 value "not a number" (NaN). bool isNegInfinity()
returns true
if this AST node has the special IEEE 754 value of negative infinity. bool isOperator()
returns true
if this AST node is an operator (e.g., +
, -
, etc.) bool isPiecewise()
returns true
if this AST node is the MathML piecewise
function. bool isRational()
returns true
if this AST node is a rational number having a numerator and a denominator. bool isReal()
returns true
if this AST node is a real number (specifically, AST_REAL_E
or AST_RATIONAL
). bool isRelational()
returns true
if this AST node is a relational operator. bool isSqrt()
returns true
if this AST node is the square-root operator bool isUMinus()
returns true
if this AST node is a unary minus. bool isUnknown()
returns true
if this AST node's type is unknown.Programs manipulating AST node structures should check the type of a given node before calling methods that return a value from the node. The following are the ASTNode object methods available for returning values from nodes:
long getInteger()
char getCharacter()
const char* getName()
long getNumerator()
long getDenominator()
double getReal()
double getMantissa()
long getExponent()
Of course, all of this would be of little use if libSBML didn't also provide methods for setting the values of AST node objects! And it does. The methods are the following:
void setCharacter(char value)
sets the value of this ASTNode to the given character value
. If character is one of +
, -
, *
, /
or ^
, the node type will be to the appropriate operator type. For all other characters, the node type will be set to AST_UNKNOWN. void setName(const char *name)
sets the value of this AST node to the given name
. The node type will be set (to AST_NAME
) only if the AST node was previously an operator (isOperator(node) != 0
) or number (isNumber(node) != 0
). This allows names to be set for AST_FUNCTIONs
and the like. void setValue(int value)
sets the value of the node to the given integer value
. Equivalent to the next method. void setValue(long value)
sets the value of the node to the given integer value
. Equivalent to the previous method. No, this is not a Gödelian self-referential loop. void setValue(long numerator, long denominator)
sets the value of this ASTNode to the given rational value
in two parts: the numerator and denominator. The node type is set to AST_RATIONAL
. void setValue(double value)
sets the value of this ASTNode to the given real (double) value
and sets the node type to AST_REAL
. void setValue(double mantissa, long exponent)
sets the value of this ASTNode to a real (double) using the two parts given: the mantissa and the exponent. The node type is set to AST_REAL_E
.Finally, ASTNode also defines some miscellaneous methods for manipulating ASTs:
ASTNode* ASTNode(ASTNodeType_t type)
creates a new ASTNode object and returns a pointer to it. The returned node will have the given type
, or a type of AST_UNKNOWN if no argument type
is explicitly given or the type code is unrecognized. unsigned int getNumChildren()
returns the number of children of this AST node or 0
is this node has no children. void addChild(ASTNode* child)
adds the given node as a child of this AST node. Child nodes are added in left-to-right order. void prependChild(ASTNode* child)
adds the given node as a child of this AST node. This method adds child nodes in right-to-left order. ASTNode* getChild(unsigned int n)
returns the n
th child of this AST node or NULL
if this node has no n
th child [i.e., if n > (node->getNumChildren() - 1)
, where node
is a pointer to a node]. ASTNode* getLeftChild()
returns the left child of this AST node. This is equivalent to getChild(0)
. ASTNode* getRightChild()
returns the right child of this AST node or NULL
if this node has no right child. void swapChildren(ASTNode *that)
swaps the children of this ASTNode with the children of that
ASTNode. void setType(ASTNodeType_t type)
sets the type of this ASTNode to the given ASTNodeType_t enumeration value.ASTNode_t* readMathMLFromString()
reads raw MathML from a text string, constructs an AST from it, then returns the root ASTNode of the resulting expression tree.Similarly, writing out Abstract Syntax Tree structures is easily done using the following method:
char* writeMathMLToString()
writes an AST to a string. The caller owns the character string returned and should free it after it is no longer needed.The example program given above demonstrate the use of these methods.