cndxparse

Creates an expression tree for later evaluation.

Declaration

PTREE cndxparse( pConvMap Schema, pTEXT Names, pTEXT InputText, NINT InputTextSize )

Description

You can use the FairCom DB expression parser/analyzer to evaluate expressions. For a complete sample program, see ctexpr.c in the ctree/source directory.

Where:

• Schema - DODA
• Names - List of names of fields
• InputText - Text of conditional expression
• InputTextSize - Length of text for conditional expression

Using the FairCom DB expression parser/analyzer involves two steps:

1. Calling cndxparse() to parse your expression, producing an expression tree the expression analyzer can evaluate. This involves three steps:
   1. Define a DODA structure.
   2. Parse the DODA into a record schema and field name list.
   3. Parse your expression to produce an expression tree.
2. Calling cndxeval() to evaluate the expression tree using data from a buffer in memory.

Return Values

Returns a PTREE parse tree on success. NULL if error.

Example

#include "ctcndx.h"  /* For PTREE type */
 
/* Define a DODA structure. */
DATOBJ doda[] = {
  {"CustomerNumber", 0,  CT_INT4U},
  {"ZipCode",        4,  CT_FSTRING,  9},
  {"State",         13,  CT_FSTRING,  2},
  {"LastName",      15,  CT_STRING,  37},
  {"FirstName",     52,  CT_STRING,  37},
  {"Address",       89,  CT_STRING,  49},
  {"City",         138,  CT_STRING,  37}
};

COUNT retval;  /* Return code.        */
pTEXT schema;  /* Record schema.      */
pTEXT names;   /* Field name list.    */
PTREE ptree;   /* Expression tree.    */
pTEXT expr;    /* Expression string.  */
 
/* Parse the DODA into a record schema and field name list. */
if ((retval = ctparsedoda(doda, 7, &schema, &names)) != 0)
    printf("Error %d parsing DODA.\n", retval);

/* Parse your expression to produce an expression tree. */
expr  = "stricmp(LastName, \"Smith\") == 0
        && CustomerNumber > 10000";
ptree = cndxparse(schema, names, expr, strlen(expr));
if (!ptree)
    printf("Error: Unable to parse expression.\n");
else
    printf("Successfully parsed expression.\n");
...

if ( ptree )
cndxfree (ptree);

See also

cndxeval, cndxfree, ctparsedoda, cndxrun, getcndxmem, putcndxmem