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Input Validation Rules: DATE, TIME, PATTERN & Filters
Concise guide to Sheerpower's VALID() rules for dates, times, expressions, menus, routines, and powerful FILTER pipelines with RESTORE for multi-step validation.

What You’ll Learn

Sheerpower’s VALID(text$, vrules$) evaluates input against readable, composable rules like date dmony, required, pattern, and more. You can also pre-process text with filter steps (trim, case-change, replace/remove, etc.) and use restore to validate both the cleaned and the original input in one pass.

Quick Reference

  • DATE DMONY — DD-Mon-YY (e.g., 01-Jan-99)
  • DATE DMONCY — DD-Mon-CCYY (e.g., 01-Jan-2000)
  • FULLTIME — CCYYMMDD HHMMSS or YYMMDD HHMMSS
  • PATTERN — Matches a rule string (see Pattern)
  • REQUIRED — Non-empty, not just spaces
  • YES/NO — Only YES, NO, Y, or N (case-insensitive)
  • VRULES — Validates the rule set itself
  • PRINTMASK — Checks a print-format mask
  • EXPRESSION — Legal Sheerpower expression
  • CODE — Legal Sheerpower code block
  • MENU — Legal INPUT MENU description
  • ROUTINE — Routine name exists
  • FILTER — ltrim, rtrim, trim, ucase, lcase, replace, remove, change; plus restore
Return Values
Most rules return TRUE (1) or FALSE (0). The fulltime rule’s documentation below states FALSE (2) as the failure value; confirm in your build. Consistently check your return values when mixing rules.

DATE DMONY — DD-Mon-YY

Checks if text$ is a legal date in DD-Mon-YY format and returns TRUE (1) or FALSE (0).

// Expect: 1 text$ = '01-Jan-99' vrule$ = 'date dmony' print valid(text$, vrule$) end

DATE DMONCY — DD-Mon-CCYY

Checks if text$ is a legal date in DD-Mon-CCYY format and returns TRUE (1) or FALSE (0).

// Expect: 1 text$ = '01-Jan-2000' vrule$ = 'date dmoncy' print valid(text$, vrule$) end

FULLTIME — Date + Time

Checks if text$ is a legal date/time in either CCYYMMDD HHMMSS or YYMMDD HHMMSS format. Returns TRUE (1) or FALSE (2).

// Expect: 1 then 1 text$ = '20000122 010101' text2$ = '990122 010101' vrule$ = 'fulltime' print valid(text$, vrule$) print valid(text2$, vrule$) end

PATTERN — Custom Rule Match

Matches text$ against a rule string. See Section 6.5.4 PATTERN(str_expr1, str_expr2) for details.

REQUIRED — Non-blank

Returns TRUE if text$ is not null and not only spaces.

// Expect: 1 then 0 text$ = 'a b c d' text2$ = ' ' vrule$ = 'required' print valid(text$, vrule$) print valid(text2$, vrule$) end

YES/NO — Strict Yes/No

Returns TRUE if text$ is one of: YES, NO, Y, N.

// Expect: 1, 1, 0 text$ = 'yes' text2$ = 'n' text3$ = 'a' vrule$ = 'yes/no' print valid(text$, vrule$) print valid(text2$, vrule$) print valid(text3$, vrule$) end

VRULES — Validate Rule Set

Checks if a vrules$ string itself is a legal set of validation rules.

// Expect: 1 print valid('integer', 'vrules') end

PRINTMASK — Format Mask

Validates that text$ is a legal print mask.

// Expect: 1 text_str$ = '##.##' vrule$ = 'printmask' print valid(text_str$, vrule$) end

EXPRESSION — Sheerpower Expression

Returns TRUE if text$ is a legal Sheerpower expression.

// Expect: 1 then 0 text_str$ = 'total = a% + 30' text_str2$ = '##~-###' vrule$ = 'expression' print valid(text_str$, vrule$) print valid(text_str2$, vrule$) end

CODE — Sheerpower Code

Returns TRUE if text$ is syntactically legal Sheerpower code.

// Expect: false path taken a$ = "print 'hello, ' name$" if not valid(a$, 'code') then print 'false' end if end

MENU — INPUT MENU Description

Validates a menu description string for use with INPUT MENU.

// Expect: 1 text_str$ = '%multi,a,b,c' vrule$ = 'menu' print valid(text_str$, vrule$) end

ROUTINE — Existence Check

TRUE if the named routine exists; FALSE otherwise.

// Expect: 1 then 0 text$ = 'do_totals' text2$ = 'test_nos' vrule$ = 'routine' print valid(text$, vrule$) print valid(text2$, vrule$) end routine do_totals: private mytotal, desc$ mytotal = 15 desc$ = 'Test Totals' print desc$; mytotal end routine

FILTER — Clean, Transform, Validate

Filters modify text$ before validation. Chain multiple steps with semicolons. Supported filters:

  • ltrim$ — remove leading spaces
  • rtrim$ — remove trailing spaces
  • trim$ — remove leading and trailing spaces
  • ucase$ — uppercase
  • lcase$ — lowercase
  • replace — replace chars: old=new, old2=new2, ...
  • remove — remove listed chars from text$
  • change — complex remap (see CHANGE$)
  • restore — restore original (pre-filter) text for later validations in the same rule chain

Examples

FILTER + REMOVE / REPLACE / TRIM

// Expect: true, true, true text$ = 'abcd10' vrules$ = 'filter remove "10"; letters' text2$ = 'ab1cd1' vrules2$ = "filter replace '1'='e'; letters" text3$ = ' 1234 ' vrules3$ = "filter trim; number" if valid(text$, vrules$) then print 'true' if valid(text2$, vrules2$) then print 'true' if valid(text3$, vrules3$) then print 'true' end

FILTER + RESTORE

Use restore when you need a filtered check and then a second check on the original text later in the chain.

// Expect: true text$ = "123" vrule$ = "filter replace '1'='a'; restore; number" if valid(text$, vrule$) then print 'true' end
Design Tip
Problem: Real-world text is messy—extra spaces, odd casing, stray characters.
Solution: Normalize with filter (trim/case/remap), then restore to re-validate the untouched original when needed.
Efficiency: A single valid() call can handle a pipeline of filters and checks—fewer passes, clearer intent.
Takeaway: Treat validation as a readable pipeline: filter ...; restore; rule; rule; ...

Putting It Together

Combine rules with semicolons to form pipelines. Validate and transform in one statement, and lean on vrules to sanity-check complex rule strings at load time.

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