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New primitives:

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* `sub' to subtract two numbers.
* `stringLength' to get the length of a string.
* `substring' to get a substring of a string.  These should be enough
  to allow most string operations to be expressed.
This commit is contained in:
Eelco Dolstra 2007-01-29 14:23:09 +00:00
parent 7dedbd896a
commit 7349bd0176
8 changed files with 88 additions and 6 deletions
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44
src/libexpr/primops.cc
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@ -723,6 +723,14 @@ static Expr primAdd(EvalState & state, const ATermVector & args)
}
static Expr primSub(EvalState & state, const ATermVector & args)
{
int i1 = evalInt(state, args[0]);
int i2 = evalInt(state, args[1]);
return makeInt(i1 - i2);
}
static Expr primLessThan(EvalState & state, const ATermVector & args)
{
int i1 = evalInt(state, args[0]);
@ -779,6 +787,36 @@ static Expr primFilterSource(EvalState & state, const ATermVector & args)
}
/*************************************************************
* String manipulation
*************************************************************/
/* `substr start len str' returns the substring of `str' starting at
character position `min(start, stringLength str)' inclusive and
ending at `min(start + len, stringLength str)'. `start' must be
non-negative. */
static Expr prim_substring(EvalState & state, const ATermVector & args)
{
int start = evalInt(state, args[0]);
int len = evalInt(state, args[1]);
PathSet context;
string s = coerceToString(state, args[2], context);
if (start < 0) throw EvalError("negative start position in `substring'");
return makeStr(string(s, start, len), context);
}
static Expr prim_stringLength(EvalState & state, const ATermVector & args)
{
PathSet context;
string s = coerceToString(state, args[0], context);
return makeInt(s.size());
}
void EvalState::addPrimOps()
{
addPrimOp("builtins", 0, primBuiltins);
@ -813,10 +851,14 @@ void EvalState::addPrimOps()
addPrimOp("removeAttrs", 2, primRemoveAttrs);
addPrimOp("relativise", 2, primRelativise);
addPrimOp("__add", 2, primAdd);
addPrimOp("__sub", 2, primSub);
addPrimOp("__lessThan", 2, primLessThan);
addPrimOp("__toFile", 2, primToFile);
addPrimOp("__filterSource", 2, primFilterSource);
addPrimOp("__substring", 3, prim_substring);
addPrimOp("__stringLength", 1, prim_stringLength);
}
}