mathexpr.h File Reference

Parsing and evaluation of mathematical expressions. More...

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Classes
struct	ExprNode

Typedefs
typedef struct ExprNode	MathExpr

Functions
MathExpr *	mathexpr_create (char *s, int(*getVar)(char *))
	Compile an infix formula into an owned postfix expression list.
double	mathexpr_eval (MathExpr *expr, double(*getVal)(int))
	Evaluate a legacy postfix expression using a local operand stack.
void	mathexpr_delete (MathExpr *expr)
	Recursively release a complete postfix MathExpr list.

Detailed Description

Parsing and evaluation of mathematical expressions.

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com (OpenSWMM maintenance and extensions)

Copyright

Copyright (c) 2026 Caleb Buahin. OpenSWMM contributions only; original EPA SWMM credits are retained.

License

Apache-2.0 for OpenSWMM contributions; original EPA SWMM provenance is retained.

Typedef Documentation

MathExpr

typedef struct ExprNode MathExpr

Function Documentation

mathexpr_create()

MathExpr * mathexpr_create	(	char *	formula,
		int(*	getVar )(char *) )

Compile an infix formula into an owned postfix expression list.

Parameters

[in]	formula	Non-null null-terminated input; identifiers and numeric literals must fit the parser's 255-byte token buffers and strlen must fit in int.
[in]	getVar	Optional synchronous variable-name-to-index callback; negative indices reject names. The temporary token pointer must not be retained.

Returns

Owned expression head to release with mathexpr_delete(), or NULL for detected syntax/parenthesis errors or an empty result.

Note

The compiled list stores values/indices and evaluates independently of the input/callback. Parsing uses shared globals and is not reentrant or thread-safe; allocation failures are not comprehensively recovered.

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mathexpr_delete()

void mathexpr_delete

(

MathExpr *

expr

)

Recursively release a complete postfix MathExpr list.

Parameters

[in]

expr

Owned list head, or NULL for no action.

Postcondition

All reachable next-linked nodes are freed. The caller must discard its original pointer; deep expressions consume recursive call-stack space.

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mathexpr_eval()

double mathexpr_eval	(	MathExpr *	expr,
		double(*	getVariableValue )(int) )

Evaluate a legacy postfix expression using a local operand stack.

Parameters

[in]	expr	Borrowed valid linked expression; NULL evaluates to zero.
[in]	getVariableValue	Optional synchronous index-to-value callback; NULL supplies zero for every variable. The callback is not retained.

Returns

Final expression value; malformed stack underflow and NaN results are mapped to zero. Infinite results are not changed.

Precondition

Expression operand counts and peak stack occupancy fit the fixed MAX_STACK_SIZE array; stack overflow is not safely recovered by this routine.

Note

The local stack permits recursive expression evaluation. Domain behavior varies by opcode: negative sqrt and nonpositive log become zero, while other illegal math may become NaN and then zero at the final check.

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