Regular expressions for numeric strings. #regex

numeric_regex.rb

# ALL THESE REQUIRE THE WHOLE STRING TO BE A NUMBER

#### NUMBERS AND DECIMALS ONLY ####
# No commas allowed
# Pass: (1000.0), (001), (.001)
# Fail: (1,000.0)
^\d*\.?\d+$

# No commas allowed
# Can't start with "."
# Pass: (0.01)
# Fail: (.01)
^(\d+\.)?\d+$

#### CURRENCY ####
# No commas allowed
# "$" optional
# Can't start with "."
# Either 0 or 2 decimal digits
# Pass: ($1000), (1.00), ($0.11)
# Fail: ($1.0), (1.), ($1.000), ($.11)
^\$?\d+(\.\d{2})?$

# Commas allowed
# "$" not allowed
# "." not allowed
# Pass: (42,000), (42000)
# Fail: ($4200), (120.00)
^(\d+|\d{1,3}(,\d{3})*)$

# Commas allowed
# Either 0 or 2 decimal digits
# "$" not allowed
# Pass: (42,000), (42000), (42,000.00), (42000.00)
# Fail: ($4200), (120.00), (00.100)
^(\d+|\d{1,3}(,\d{3})*)(\.\d{2})?$

#### COMMA-GROUPED ####
# Commas required between powers of 1,000
# Can't start with "."
# Pass: (1,000,000), (0.001)
# Fail: (1000000), (1,00,00,00), (.001)
^\d{1,3}(,\d{3})*(\.\d+)?$

# Commas required
# Cannot be empty
# Pass: (1,000.100), (.001)
# Fail: (1000), ()
^(?=.)(\d{1,3}(,\d{3})*)?(\.\d+)?$

# Commas optional as long as they're consistent
# Can't start with "."
# Pass: (1,000,000), (1000000)
# Fail: (10000,000), (1,00,00)
^(\d+|\d{1,3}(,\d{3})*)(\.\d+)?$

#### LEADING AND TRAILING ZEROES ####
# No commas allowed
# Can't start with "."
# No leading zeroes in integer part
# Pass: (1.00), (0.00)
# Fail: (001)
^([1-9]\d*|0)(\.\d+)?$

# No commas allowed
# Can't start with "."
# No trailing zeroes in decimal part
# Pass: (1), (0.1)
# Fail: (1.00), (0.1000)
^\d+(\.\d*[1-9])?$