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>find-first-char</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1486"
></A
><H2
>Name</H2
>find-first-char -- Find the first occurance of a character in a string</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1489"
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><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>(find-first-char string skipchars findchars #!optional (pos 0))</PRE
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><A
NAME="AEN1492"
></A
><H2
>Description</H2
><P
>Finds first character in <TT
CLASS="LITERAL"
>string</TT
> that is in <TT
CLASS="LITERAL"
>findchars</TT
>, skipping all
occurances of characters in <TT
CLASS="LITERAL"
>skipchars</TT
>. Search begins at <TT
CLASS="LITERAL"
>pos</TT
>. If
no such characters are found, returns -1.</P
><P
>If skipchars is empty, skip anything not in findchars
If skipchars is #f, skip nothing
If findchars is empty, the first character not in skipchars is matched
It is an error if findchars is not a string.
It is an error if findchars is empty and skipchars is not a non-empty
string.</P
></DIV
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CLASS="REFSECT1"
><A
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><H2
>Author</H2
><P
>Norman Walsh, <ndw@nwalsh.com></P
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CLASS="REFSECT1"
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NAME="AEN1503"
></A
><H2
>Source Code</H2
><PRE
CLASS="PROGRAMLISTING"
>(define (find-first-char string skipchars findchars #!optional (pos 0))
;; Find the first occurance of a character in a string
(let ((skiplist (if (string? skipchars)
(string->list skipchars)
'()))
(findlist (string->list findchars)))
(if (and (null? skiplist) (null? findlist))
;; this is an error
-2
(if (or (>= pos (string-length string)) (< pos 0))
-1
(let ((ch (string-ref string pos)))
(if (null? skiplist)
;; try to find first
(if (member ch findlist)
pos
(if (string? skipchars)
(find-first-char string
skipchars findchars (+ 1 pos))
-1))
;; try to skip first
(if (member ch skiplist)
(find-first-char string skipchars findchars (+ 1 pos))
(if (or (member ch findlist) (null? findlist))
pos
-1))))))))</PRE
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