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check 

        # StringScanner.check

(from ruby core)
---
    check(pattern)

---

This returns the value that #scan would return, without advancing the
scan pointer.  The match register is affected, though.

    s = StringScanner.new("Fri Dec 12 1975 14:39")
    s.check /Fri/               # -> "Fri"
    s.pos                       # -> 0
    s.matched                   # -> "Fri"
    s.check /12/                # -> nil
    s.matched                   # -> nil

Mnemonic: it "checks" to see whether a #scan will return a value.

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.