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Decapitalize

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description

Decapitalize["string"]

Gives "string" with its first character in lowercase.

Decapitalize[{s1, s2, ...}]

Decapitalizes each string.

Examples (10)

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (3)

In[1]:= Capitalize["hello world"]
Out[1]= "Hello world"

In[2]:= Capitalize["élan"]
Out[2]= "Élan"

In[3]:= Decapitalize[{"Alpha", "Beta"}]
Out[3]= {"alpha", "beta"}

Applications (7)

In[4]:= Decapitalize["Hello World"]
Out[4]= "hello World"

Only the first character is lowered

In[5]:= Decapitalize["ABC"]
Out[5]= "aBC"

In[6]:= Decapitalize["ÉCOLE"]
Out[6]= "éCOLE"

In[7]:= Decapitalize["Ωmega"]
Out[7]= "ωmega"

A list of strings maps

In[8]:= Decapitalize[{"Alpha", "Beta"}]
Out[8]= {"alpha", "beta"}

A non-letter first character is unchanged

In[9]:= Decapitalize["123abc"]
Out[9]= "123abc"

A list with a non-string: Decapitalize::strse

In[10]:= Decapitalize[{"Alpha", 1}]
Out[10]= Decapitalize[{"Alpha", 1}]

Implementation notes

Algorithm. builtin_decapitalize calls capitalize_builtin(res, "Decapitalize", 0). A String argument goes to the shared case kernel map_case(s, len, 0, 0, 1) — the same routine as ToLowerCase, restricted by its from/count window to character 0, so only the first code point is looked up in k_lower_map and every later byte is copied verbatim. A flat List of strings (checked by is_string_list) is mapped element by element into a new List; anything else emits Decapitalize::strse through strings_arg_message (the mth_message funnel) and stays unevaluated.

Data structures. The generated full-case-mapping table k_lower_map (U8CaseMap records, Unicode 16.0.0, from tools/gen_unicode_tables.py), searched by binary search; ASCII is mapped inline. The first character may expand to up to three code points (Decapitalize["İ"] gives i plus U+0307`).

Complexity / limits. One O(L) copy of the string plus one O(log M) table lookup. It applies the lowercase mapping, not Unicode titlecasing. Not Listable: nested or mixed lists are rejected rather than threaded. No numeric (packed / Compile[]) surface.

Attributes: Protected.

References

See also: Capitalize

Notes & additional examples

Notes

  • Lowercases the first character with the full Unicode table used by ToLowerCase; everything after it is copied unchanged.
  • Accepts a string or a flat list of strings (not Listable); anything else emits Decapitalize::strse and stays unevaluated.
  • Attributes {Protected}.
  • See also: Capitalize, ToLowerCase.