1. An audio decoder for providing a decoded audio information on the basis of an encoded audio information, the audio decoder comprising: an arithmetic decoder for providing a plurality of decoded spectral values on the basis of an arithmetically encoded representation of the spectral values comprised in the encoded audio information; and a frequency-domain-to-time-domain converter for providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information; wherein the arithmetic decoder is configured to select a mapping rule describing a mapping of a code value of the arithmetically-encoded representation of spectral values onto a symbol code representing one or more of the decoded spectral values, or at least a portion of one or more of the decoded spectral values in dependence on a context state described by a numeric current context value; wherein the arithmetic decoder is configured to determine the numeric current context value in dependence on a plurality of previously decoded spectral values; wherein the arithmetic decoder is configured to evaluate a hash table, entries of which define both significant state values amongst the numeric context values and boundaries of intervals of non-significant state values amongst the numeric context values, in order to select the mapping rule, wherein a mapping rule index value is individually associated to a numeric context value being a significant state value, and wherein a common mapping rule index value is associated to different numeric context values laying within one of said intervals bounded by said interval boundaries.